Route server on a Bird2.0.2
Alexander Zubkov
green at qrator.net
Fri Dec 14 23:29:54 CET 2018
In my setup everything is ok. I made 4 namespaces for peera, peerb,
rs1 and rs2 and joined them with one bridge network.
Here is route views on client networks. As you can see - the next hop
is ok on them.
peera:
bird> show route all
Table master4:
192.168.2.0/24 unicast [direct1 00:49:56.054] * (240)
dev veth0
Type: device univ
10.0.2.0/24 unicast [bgp1 01:26:25.953 from 192.168.2.1] *
(100) [AS65124i]
via 192.168.2.47 on veth0
Type: BGP univ
BGP.origin: IGP
BGP.as_path: 65001 65124
BGP.next_hop: 192.168.2.47
BGP.local_pref: 100
10.0.1.0/24 unicast [s1 01:06:02.606] * (200)
dev lo
Type: static univ
peerb:
bird> show route all
Table master4:
192.168.2.0/24 unicast [direct1 00:51:01.757] * (240)
dev veth0
Type: device univ
10.0.2.0/24 unicast [s1 01:11:43.140] * (200)
dev lo
Type: static univ
10.0.1.0/24 unicast [bgp1 01:27:14.489 from 192.168.2.2] *
(100) [AS65123i]
via 192.168.2.45 on veth0
Type: BGP univ
BGP.origin: IGP
BGP.as_path: 65123
BGP.next_hop: 192.168.2.45
BGP.local_pref: 100
The only issue here is that bird2 will prepend as on the path peerb ->
rs2 -> rs1 -> peera. That logic I have already asked to fix in this
mailing list.
On Fri, Dec 14, 2018 at 10:15 PM Noémie Clémençon
<nclemencon at rezopole.net> wrote:
>
> Configuration toward client :
>
> protocol bgp PeerA {
> local as 65001;
> passive on;
> neighbor 192.168.2.45 as 65123;
> default bgp_local_pref 1000;
> ipv4 {
> import keep filtered on;
> import limit 1001 action disable;
> receive limit 1001 action disable;
> export filter {ix_out_rs(id,65123);};
> import filter {clear_no_export();community_in();pfx65123_v4_in();reject;};
> };
> rs client;
> }
>
>
> Configuration between RS (on bird 2.0.2)
>
> protocol bgp RS2 {
> local as 65001;
> neighbor 192.168.2.2 as 65001;
> direct;
> ipv4 {
> import filter rs_in;
> import keep filtered;
> gateway direct;
> export filter rs_out;
> };
> }
>
>
> Configuration between RS (on bird 1.6.3)
>
> protocol bgp RS1 {
> local as 65001;
> neighbor 192.168.2.1 as 65001;
> import filter rs_in;
> export filter rs_out;
> }
>
> I didn't include the filters, since they are only used to add/remove community or exclude prefixes.
>
> Thanks for the help,
> Noémie
>
> On 14/12/2018 20:17, Alexander Zubkov wrote:
>
> Hi,
>
> What configs are you using towards client and between route servers on
> both sides?
> On Fri, Dec 14, 2018 at 7:02 PM Noémie Clémençon
> <nclemencon at rezopole.net> wrote:
>
> Hi all,
>
> We are using Bird v2.0.2 as a route-server, and I have a question about the use of i-BGP sessions on a Bird RS.
>
> We have the following topology : 2 RS (RS1 and RS2) are connected to several peers, and some of those peers are connected to only one RS.
> In order to get the same amount of prefixes on both RS, a i-BGP session was created between RS1 and RS2.
>
> i-BGP
> RS1 ----------------- RS2
> | |
> | |
> Peer1 Peer2
>
>
>
> This topology was working really well between a Bird 1.6.3 and a Cisco ASR, and we were able to announce the prefixes without the RS AS
> in the AS-Path and with the proper next-hop regardless of from where the prefixes were learnt (RS1 or RS2).
> To clarify, if Peer1 was peering with RS1, and learning the prefixes of someone, Peer2, who was peering exclusively with RS2, Peer1 would get the prefixes
> with the as path starting with the AS of peer2 and the next-hop would be peer2 router IP.
>
> We wanted to use the same topology with a Bird 2.0.2 in place of a ASR, but it seems to be treating i-BGP prefixes differently. With a bird 2.0.2, Peer1 is receiving
> the prefixes from Peer2 however the prefixes are announced with the RS AS in the AS path and the next hop is the RS1 IP, hence the prefixes were unusable by Peer1.
>
> We are using the following tweak to correct the next hop : the use of 'direct' and 'gateway direct' has corrected the next hop IP.
> Below an example of the configuration we used.
> We still haven't found a solution for the AS path.
>
> protocol bgp RS1 {
> local as 65001;
> neighbor 192.168.2.1 as 65001;
> ...
> direct;
> ipv4 {
> import ...;
> gateway direct;
> export ...;
> };
> }
>
> Since we never noticed this problem for bird 1.6.3, is this a different behavior for Bird 2.0.2 ?
> Or is there a better way to have the intended announcements on both RS ?
> I-BGP sessions between RS are really handy in case of failure, and we would like to keep this topology.
>
>
> Kind regards,
> Noémie
>
>
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